HEAD “We can’t go this hard any more.”
Your brain’s primary job is to protect you, says exercise scientist Tim Noakes, MD—which is why it can force you to slow down even when you still have fuel in the tank and fresh muscle fibers in your legs.

PLAY MIND GAMES: “Your brain calculates within the first meters whether it’s going to be a good day,” says Noakes. “Decide out of the gate that you’re going to do it.” Once you start doubting, you’re good as done.

STOMACH “I will commit mutiny if you guzzle more sports drink.”Drinks that contain fructose are usually the culprit. Fructose isn’t as rapidly absorbed as other sugars, says dietitian Donna Marlor, RD. Too much can cause gas, bloating, or diarrhea.

READ LABELS: Look for beverages that contain about 39 to 54 grams of sugar per 24-ounce bottle. And aim for a mixture of carbs: You want a drink that lists glucose (or maltodextrin) before fructose.

FEET “I need wiggle room.” Cycling shoes are meant to be snug so your feet stay put and transfer power directly into your pedals. But feet are a cluster of sensitive nerves, and prone to hot spots, numbness, and pain.

SOLE STRATEGY: Look for shoes with a higher, wider toe box. Place metatarsal inserts just behind the ball of the foot to spread the bones and keep nerves from pinching.